Vitamin D deficiency is very common among children with critical illnesses, and it is associated with worse outcomes, according to new research.

A recent study -- published in the European Journal of Clinical Nutrition -- revealed that adults with low vitamin D levels have a 30% greater risk of death than people who had higher levels. New research suggests that children are also likely to experience illness with low vitamin D levels.

Children with serious and critical illnesses are more likely to be ill for longer, and experience more severe illness if they are deficient in vitamin D, according to the findings of two new research papers.

The studies -- both published in Pediatrics -- reveal that 40% of children admitted into a hospital's paediatric intensive care unit (PICU) over a 12-month period were deficient in the sunshine vitamin, and that deficiency is directly associated with longer hospital stays and more severe illness.

Kate Madden, lead author of one of the studies noted that whilst earlier research has linked low levels of the vitamin with worse outcomes in critically ill adults, the new findings suggest that the same thing may be true for children, researchers say.

However, she noted that it is not yet clear if screening sick children for vitamin D deficiency and treating those who are deficient with supplements will help to improve outcomes.

"We certainly think this is something that deserves further study," said Madden, of Harvard Medical School, USA.

Study details

In the first study -- led by Madden -- researchers screened 511 children admitted to the PICU of a US hospital over a 12-month period. The team found that 2 in 5 children (40%) were deficient in vitamin D.

"We found a high rate of vitamin D deficiency in critically ill children," reveal Madden and her colleagues.

In the second study, led by Dr James Dayre McNally, from the University of Ottawa, researchers collected data from 326 critically ill children and teenagers.

In the study, McNally and his team reveal that almost 70% of the children admitted were deficient in vitamin D when tested. The team also revealed that the level of deficiency was independently associated with longer ICU stays and more severe illness.

"Vitamin D deficiency was independently associated with a longer PICU length of stay and increasing severity of illness as determined by the Pediatric Risk of Mortality score with every additional point increasing the likelihood of being vitamin D deficient by 8%," say McNally and his colleagues.

Both studies, show vitamin D deficiency to be considerably more than has been reported in healthy children and adolescents.